All Bugs are planned to be resolved
This was not actually a bug of FABulator, but a bug of the geometry_generator in FABulous. It was resolved for all tested fabrics by a fix. However, fabrics with larger supertiles of at least width or height 3 will need to be tested.
The bug has been resolved by a fix for all tested fabrics. Further testing will need to be done to make sure of it being fully resolved.
This can happen because the whole (geometric) information of a fabric is held in RAM at all times (even when parts are not currently needed). This will be changed in the future, as it is very restricting on the size of importable fabrics. If your machine has enough RAM, it can be resolved by increasing the JVM heap size.
To increase the heap size to, say, 8 Gigabytes, one can add
<options>
<option>-Xmx8g</option>
</options>
in the pom.xml file right after the line containing
<mainClass>FABulator/fabulator.FABulator</mainClass>
in the javafx-maven-plugin section.
To check if the error is resolved, run the application
as usual with mvn javafx:run